A method and apparatus for rotating a portion or segment of a casing string in a relatively highly deflected well bore. A straight well bore portion is provided adjacent the completion interval, beyond the deflected portion. A casing string is made up with a segment connected by a swivel to the remainder of the string. This segment is located in the straight portion of the bore. A drill string is lowered into the casing into engagment with a rotatable swivel portion fixed to the casing segment. The drill string is rotated to rotate the casing segment independently of the remainder of the casing string. This facilitates removal of excess mud cake from the annulus adjacent the casing segment, and also placement of cement in the annulus.